#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	
	double b = 0;
	double ret = 0;
	int flag = 1;
	for (b = 1.0; b < 100; b++)
	{
		if ((int)b % 2 == 0)
		{
			flag = -1;
			ret+=flag * (1 / b);

		}
		else
		{
			flag = 1;
			ret += flag * (1 / b);

		}
		
	}
	printf("%lf", ret);
	return 0;
}